Process for increasing the scratch resistance of glass



Dec. 15, 1964 R. H. DETTRE 3,161,535 PROCESS FOR INCREASING THE SCRATCH RESISTANCE 0F GLASS Filed Dec. 22, 1961 FIG. I F I G. 2

APPLY SOLUTION OF HEAT CLASS TO APPROXI- TITANIUM COMPOUND MATELY ITS ANNEALIIIC TO'CLASS SURFACE TEMPERATURE HEAT GLASS TO APPROXI- APPLY VAPORS OF NATELY ITS ANNEALINC TITANIUM COMPOUND TEMPERATURE T0 HEATED CLASS COOL CLASS TO COOL CLASS TO LESS THAN IOOC LESS THAN IDOC APPLY SATURATED L- APPLY SATURATED ALI- PHATIC CARBONYL PH C CARBONYL COM- POUND IMMEDIATELY TO PO IMMEDIATELY TO CLASS SURFACE CLASS SURFACE INVENTOR ROBERT mow Mm:

ATTORNEY United States Patent 3,161,535 PROCESS FOR INCREASTNG THE SCRATCH RESlSTANCE 0F GLASS Robert Harold Dettre, Brandywine Hundred, Del, as-

signor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Dec. 22, 1961, Ser. No. 161,415 5 Claims. (Cl. 117-69) This invention relates to an improved process for increasing the scratch resistance of glass bodies.

The problem and importance of scratch resistance in glass are discussed in detail by Deyrup in US. Patent 2,831,780. It is a practical industrial problem and relates to such items as the weakening of glass bottles by rubbing against each other in transit, the marring of window glass through scratches by impinging dust or glass fragments, and the weakening of textile glass fibers by mutual abrasion.

In said patent, Deyrup offers a method for overcoming this deficiency of glass by treating the same with the vapors of a metallo-organic compound at a temperature between the lowest annealing temperatureof glass and the temperature at which excessive deformation occurs.

In copending application Serial No. 58,616 (now US. Patent 3,051,593) and U.S. Patent No. 3,004,863 of C. L. Gray and R. H. Dettre, processes are described and claimed wherein glass articles are treated with an aqueous solution of certain water-soluble and water-stable ester derivatives of titanium, following which the glass articles are passed through an annealing oven wherein they are heated to a temperature at or near the annealing point, and then allowed to cool to' essentially room temperature. Still a third type of titanium compounds is employed in copending application of Brockett, Dettre and Gray, Serial No. 97,757, filed March 23, 1961, now Patent No. 3,130,071. l I

All these processes have the one feature in common that a titanium oxide film is eventually formed in contact with the glass surface which is probably bonded, partially or completely, with the material of the glass through Ti-OSi links.

As a final step, however, in all the aforegoing processes the articles must be allowed to stand in open :air for a period not less than 20 or 30 minutes. Until after this standing period in air, the scratch resistance effect does 7 not seem to develop fully. And although Deyrup has not recognized or taught it in his patent, a standing period in air is essential in his process, too, if a complete and reliable development of the scratch resistant effect is desired.

As has been pointed out in US. Patent 3,051,593, the standing in open air for 20 minutes before use is apt to occur automatically with almost any glass article. Nevertheless, the standing step takes on a positive aspect, often with uneconomical side features, when one considers belt line production of articles such as milk bottles. The standing step demands that the belt line be held still for 20 minutes or'more so as not to give the bottles a chance to scratch each other in motion before their scratch-resistant coating has become fixed. Where the article produced must be of relatively small cost, such holding up period becomes a matter of material economic significance.

Furthermore, the required length of the standing period may vary from one treatment to another (depending on the type of titanium compound selected for the treatment and perhaps also on the temperature and mode of application of the annealing treatment) and therefore often presents problems in control of the process, inasmuch as one cannot readily determine by mere inspection of the articles whether they have or have not received the proper length of air-curing.

3,161,535 Patented Dec. 15, 1964 ice It is accordingly an object of this invention to modify the aforementioned processes of imparting scratch resistance of glass bodies, whereby to eliminate the need of holding the treated bodies still in air for a determined period of time after annealing, and to substitute therefor a 7 positive chemical treatment. Other objects and achievements of this invention will become apparent as the description proceeds.

Now, according to my present invention, the curing period is replaced by a treatment with certain chemical agents as defined below, which treatment can be achieved quickly by immersion, spraying or otherwise coating the annealed glass article with an organic solvent solution, a melt or even vapors of said chemical agents.

Reference is made to the attached drawing which illustrates by a flow sheet diagram the process of the present invention.

FIGS. 1 and 2 are alternative processes which differ only with respect to the manner of applying the titanium organic compound. In FIG. 1, a solution of the titanium compound is applied to the glass .prior to heating; whereas, in the alternative process of FIG. 2, vapors of a titanium compound are applied to the heated glass. The last two steps in the processes of both FIGS. 1 and 2 are the same.

I have found that glass articles which have been treated with organic titanium compounds and annealed according to the aforementioned patents and copending application become satisfactorily scratch resistant if the annealing is followed up with a step of treating said articles with an aliphatic compound containing a C=O group and an alkyl chain of at least 9 C-atoms attached to the C- atom of said group. More particularly, the applicable agent for this invention may be A saturated carboxy acid, for instance, capric, lauric, myristic, palrnitic, stearic, a rachidic or behenic;

An aldehyde, for instance, dodecanal, tetradecanal, hexadecanal, octadecanal or eicosanal; or

A ketone, such as methyl dodecyl vketone, methyl hexadecyl ketone methyl octadecyl ketone, dodecyl propyl ketone and octadecyl butyl ketone.

The application of the above compounds to glass in accordance with this invention may be achieved by three distinct methods. v

All three start with a titania coated glass article" obtained by the method of said Deyrup patent, said Gray and Dettre patents or said copending application. The coated glass surface is then either (1) dipped into an organic solvent solution of one of the above defined compounds, (2) dipped into a liquid melt of one of these compounds, .or (3) exposed to the vapors of one of these compounds. Of course, mixtures of compounds may also be used. When using the vapor method, it is not necessary that the agent be at reflux temperature; inasmuch as there is sufiicient material present in vapor form over a melt to complete the process. 1 The vapor method is, however, somewhat slower than the other two and the latter are. therefore preferred. H

7 Typical commercial operations, including application of the titania coating, are illustrated in the following examples.

EXAMPLE I Organic Solution cooled slowly to near ambient temperatures. On issuing from the lehr, the bottles are dipped into (or sprayed with) a 0.25% solution of lauric acid in cetane and allowed to drain.

The bottles thus obtained are immediately scratch resistant as may be demonstrated by rubbing two such botties together with no apparent effect. (If two bottles are rubbed together immediately after leaving the lehr but before treatment with the above solution, they scratch each other readily.)

The lauric acid solution used above may be replaced with any one of the following solutions with equally successful results.

Compound Solvent Concentration,

percent Behenic Acid Cetane 0.25 Dodecanal (Lauraldehyde) Ddecane 1.0

The glass objects treated with nonaqueous solutions are rinsed with water. This merely removes any excess material which may be present and is not essential to the process.

EXAMPLE II Melt Using the procedure of Example I for forming the titani-a coating on the glass suruface, the glass articles are removed from the lehr on reaching the melt temperature of one of the compounds indicated below and dipped into a melt of said compound. They are then allowed to drain and cool, if necessary, and are rinsed with water. The glass surfaces are immediately scratch resistant.

It will be noted that the melt temperatures vary considerably, and the temperatures to which the glass objects are cooled in the lehr before curing are correspondingly varied.

EXAMPLE III Vapor Using the procedure described in Examplel for forming the titania coating on the glass surfaces, the cooled bottles are passed slowly over a vessel which contains one of the following materials at the temperature indi cated. The bottles are then cooled, rinsed with water and are immediately scratch resistant. Again, the water rinse is not an essential part of the process.

Compound: Temperature, C. Behenic acid 205 Myristic acid 142 Lauric acid 160 Margaric acid 140 Pelargonic acid 152 Dodecanal (lauraldehyde) 140 Tetradecanal (myristaldehyde) 130 Dodecylpropyl ketone 160 In the above examples, the treatment prior to annealing was done with triethanolamine titanate, in accordance with US. Patent 3,051,593 to Gray and Dettre. Equally successful results are obtained if this treatment is done with an aqueous solution of diisopropyl diacetoacetonyl titanate (as in the Gray and Dettre patent, No. 3,004,638),

invention.

As an added advantage of the treatment constituting this invention, it has been found that glass articles produced by the present process are more scratch resistant than those produced by the methods of the aforementioned patents and copending application, even though the aircuring step above described has been applied to the titanium-treated glass.

The resistance to scratching of a glass surface can be measured by drawing a glass rod across the surface and measuring the weight or tension which must be applied to the rod to produce a scratch. In this manner, the higher scratch resistance produced by the present process can be readily demonstrated.

Treatment with the special agents of this invention of a glass object which does not have a preformed titania coating with the compounds defined in the aforementioned patents or in said copending application imparts to said glass objects -a hydrophobic surface but not scratch resistance to any degree.

The scratch resistant glass surfaces produced according to the present invention are durable to washing with water, but not to washing with aqueous solutions of anionic detergents, such as the alkali metal salts of long chain alkyl sulfates or alkyl or alkaryl sulfonates. However, where an article has been washed with such a detergent, the scratch-resistant surface thereon can be reformed by treating the article again, in one of the aforegoing manners, with one of the agents mentioned in this specification. (In other words, the curing treatment is repeated on the Washed article, but there is no need for repeating the treatment with a titanium ester or the annealing operation.)

It will be understood that the details of procedure above set forth may be varied widely within the skill of those engaged in this art.

For instance, the temperature to which the glass is allowed to cool in the annealing lehr need not drop below the temperature at which the curing treatment is intended to be applied, and may indeed be considerably higher so long as there is no danger of shattering the glass object by abrupt cooling during the curing treatment. Altogether, the various modes of application of the curing treatment of this invention may vary in temperature from room temperature to 205 C., while the temperature of the glass just prior to the curing treatment may be some 50 C. higher than the temperature of the applied solution, melt or vapor.

In lieu of cetane or dodecane in the procedure of Example I, any economically available organic liquid may be employed which dissolves the particular curing agent selected. In general, the higher boiling hydrocarbons are the preferred organic solvents, but others, such as alcohols and acetone, can be used, provided that the curing agent is soluble therein. The vapor pressure of an agent used in the vapor treatment need not be high; 0.1 atm. is generally sufficient, but higher vapor pressures can be used and usually will be found to speed up the process.

I claim as my invention:

1. In a process for increasing the scratch resistance of glass by applying an organo-titanium compound to the surface of the glass, which is in non-fibrous form, heating the glass, and then allowing the glass to stand in air for a period of not less than 20 minutes to develop the desired scratch resistance, the improvement which comprises eliminating the standing period required to develop scratch resistance by coating the surface of the glass, immediately after the heating step and at a temperature between room temperature and 205 C., with an aliphatic compound selected from the group consisting of unsubstituted, saturated aliphatic aldehydes, unsubstituted, saturated aliphatic ketones, and unsubstituted, saturated aliphatic carboxylic acids, containing a maximum of 23 carbon atoms in an aliphatic chain of at least 9 carbon atoms.

2. The process of claim 1 wherein the aliphatic compound is lauric acid.

3. The process of claim 1 wherein the aliphatic compound is applied to the glass from a solution of said compound in an organic solvent.

4. The process of claim 1 wherein the aliphatic com pound is applied to the glass in molten form.

5. The process of claim 1 wherein the aliphatic compound is applied to the glass in vapor form.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A PROCESS FOR INCREASING THE SCRATCH RESISTANCE OF GLASS BY APPLYING AN ORGANO-TITANIUM COMPOUND TO THE SURFACE OF THE GLASS, WHICH IS IN NON-FIBROUS FORM, HEATING THE GLASS, AND THEN ALLOWING THE GLASS TO STAND IN AIR FOR A PERIOD OF NOT LESS THAN 20 MINUTES TO DEVELOP THE DESIRED SCRATCH RESISTANCE, THE IMPROVEMENT WHICH COMPRISES ELIMINATING THE STANDING PERIOD REQUIRED TO DEVELOP SCRATCH RESISTANCE BY COATING THE SURFACE OF THE GLASS, IMMEDIATELY AFTER THE HEATING STEP AND AT A TEMPERATURE BETWEEN ROOM TEMPERATURE AND 205*C., WITH AN ALIPHATIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF UNSUBSTITUTED, SATURATED ALIPHATIC ALDEHYDS, UNSUBSTITUTED, SATURATED ALIPHATIIC KETONES, AND UNSUBSTITUTED, SATURATED ALIPHATIC CARBOXTIYLIC ACIDS, CONTAINING A MAXIMUM OF 23 CARBON ATOMS IN AN ALIPHATIC CHAIN OF AT LEAST 9 CARBON ATOMS. 